Aluminum nitride substrate

Abstract

A printed circuit board may include an aluminum nitride (AIN) substrate that includes an AIN thin film and a layer of high-frequency polymer as a carrier substrate of the AIN thin film. The AIN substrate forms a first layer of the printed circuit board. The AIN substrate comprises a heat spreader that laterally spreads out heat from a heat sink on the printed circuit board to form a thermal dissipation path parallel with a signal path on the printed circuit board. The printed circuit board may include a main substrate aligned to and bonded with the AIN substrate. The main substrate may include one or more additional layers of the printed circuit board.

What is claimed is: 
     
       1. A semi-rigid or flexible double-sided multi-layer printed circuit board that is sequentially laminated and suitable for wire bonding and surface mount assembly, the printed circuit board comprising:
 an aluminum nitride (AIN) substrate that includes:
 an AIN thin film; and 
 a layer of high-frequency polymer as a carrier substrate of the AIN thin film, wherein: 
 the AIN substrate forms a first layer of the printed circuit board; 
 the AIN substrate comprises a heat spreader that laterally spreads out heat from a heat sink on the printed circuit board to form a thermal dissipation path parallel with a signal path on the printed circuit board; and 
 
 a main substrate aligned to and bonded with the AIN substrate, the main substrate including one or more additional layers of the printed circuit board. 
 
     
     
       2. The printed circuit board of  claim 1 , further comprising a thermosetting conductive bonding film that bonds the AIN substrate to the main substrate. 
     
     
       3. The printed circuit board of  claim 2 , wherein:
 the AIN substrate includes a first via; 
 the main substrate includes a second via; 
 the thermosetting conductive bonding film includes a conductive path that is electrically conductive, thermally conductive, or both electrically and thermally conductive, wherein the conductive path is electrically conductive in a vertical direction, allowing a via transitioning from the first via to the second via; and 
 the first via in the AIN substrate is coupled to the second via in the main substrate through the conductive path in the thermosetting conductive bonding film. 
 
     
     
       4. The printed circuit board of  claim 1 , further comprising a layer of pre-impregnated composite film materials that bond the AIN substrate with the main substrate. 
     
     
       5. The printed circuit board of  claim 1 , wherein the AIN thin film includes nitrogen content with a particular nitrogen concentration level and is free of fiber weave materials. 
     
     
       6. The printed circuit board of  claim 1 , wherein the AIN substrate includes a first loss tangent that is lower than a second loss tangent of fiber weave materials. 
     
     
       7. The printed circuit board of  claim 1 , wherein the AIN substrate includes a thickness between 1 micrometer and 100 micrometers. 
     
     
       8. The printed circuit board of  claim 1 , wherein the high-frequency polymer includes one of polyimide and kapton. 
     
     
       9. The printed circuit board of  claim 1 , wherein the first layer of the printed circuit board that includes the AIN substrate comprises one of a top layer, a bottom layer, or a core layer of the printed circuit board. 
     
     
       10. The printed circuit board of  claim 1 , wherein a lateral spread of heat by the AIN substrate comprising the heat spreader avoids loss of routing space within the printed circuit board. 
     
     
       11. The printed circuit board of  claim 1 , further comprising an optical waveguide that includes at least a portion of the AIN substrate surrounded by dielectric material with an index of refraction different from the AIN thin film. 
     
     
       12. The printed circuit board of  claim 1 , wherein the first layer of the printed circuit board that includes the AIN substrate comprises a top layer of the printed circuit board with a thickness no greater than 150 micrometers, and a top side of the printed circuit board includes traces with a width between about 10 micrometers and about 65 micrometers and trace pitches with a width between about 15 micrometers and 200 micrometers. 
     
     
       13. The printed circuit board of  claim 1 , wherein the AIN substrate includes a metallization of one of nickel (Ni)-based deposition, palladium-based deposition, silver-based deposition, Ni-chrome-electro-vacuum deposition, Tin palladium colloid electro less deposition, and Ni—P electro less deposition. 
     
     
       14. The printed circuit board of  claim 1 , wherein the AIN substrate includes a stack-up of the AIN thin film, the layer of high-frequency polymer, and one or more of a plating, a first patterned mask, a layer of electrolytic copper, a layer of metal deposition, a second patterned mask, or a layer of cladding copper. 
     
     
       15. The printed circuit board of  claim 14 , wherein the plating includes electro less nickel electro less palladium immersion gold (ENEPIG) plating. 
     
     
       16. A semi-rigid or flexible double-sided multi-layer printed circuit board that is sequentially laminated and suitable for wire bonding and surface mount assembly, the printed circuit board comprising:
 an aluminum nitride (AIN) substrate that includes:
 a layer of cladding copper; 
 an AIN thin film disposed on top of the layer of cladding copper; and 
 a layer of high-frequency polymer disposed on top of the AIN thin film, wherein: 
 the AIN substrate forms a first layer of the printed circuit board; and 
 the AIN substrate comprises a heat spreader that laterally spreads out heat from a heat sink on the printed circuit board to form a thermal dissipation path parallel with a signal path on the printed circuit board; and 
 
 a main substrate aligned to and bonded with the AIN substrate, the main substrate including one or more additional layers of the printed circuit board. 
 
     
     
       17. An optical waveguide comprising:
 a layer of high-frequency polymer; 
 a first aluminum nitride (AIN) thin film disposed on top of the layer of high-frequency polymer, the first AIN thin film including nitrogen content with a first nitrogen concentration level and a first index of refraction; and 
 a second AIN thin film embedded in the first AIN thin film, the second AIN thin film including nitrogen content with a second nitrogen concentration level and a second index of refraction, wherein: 
 the first nitrogen concentration level is lower than the second nitrogen concentration level; 
 the first index of refraction is lower than the second index of refraction; and 
 the second AIN thin film is embedded in the first AIN thin film to guide a light beam to propagate through the second AIN thin film. 
 
     
     
       18. The optical waveguide of  claim 17 , wherein the first AIN thin film and the second AIN thin film form a trench waveguide. 
     
     
       19. The optical waveguide of  claim 17 , wherein the second AIN thin film is selectively etched to form an etched Bragg grating configured to reflect or transmit an optical signal with a particular wavelength. 
     
     
       20. The optical waveguide of  claim 17 , wherein the second AIN thin film is selectively etched to form distributed Bragg reflectors that operate as a wavelength division multiplexing (WDM) filter.